Apparatus for determination of the orientation of a moving member,particularly a drilling head

ABSTRACT

APPARATUS FOR DETERMINING THE PHYSICAL ORIENTATION OF A MOVING MEMBER, SUCH AS A DRILLING HEAD USED IN WELL DRILLING INCLUDING A PAIR OF PENKULUM UNITS CARRIED BY THE MOVING MEMBER, EACH BEING MOUNTED ORTHOGONALLY TO THE OTHER AND TO THE VERTICAL AXIS OF THE MEMBER, AND EACH ADAPTED TO TRANSMIT A SIGNAL REPRESENTATIVE OF ANGULAR INCLINATION TO THE HORIZONTAL. AN AZIMUTHAL DIRECTION SENSING DEVICE PROVIDES A SIGNAL REPESENTATIVE OF THE AZIMUTHAL ORIENTATION OF A PIVOT AXIS OF ONE OF THE PENDULUM UNITS. CALCULATING MEANS AND RELATED INSTRUMENTATION PROVIDE A RESULTANT SIGNAL REPRESENTATIVE OF THE AMOUNT AND DIRECTION OF INCLINATION OF THE MEMBER.

United States Patent Pierre Schnerb lnventor [56] ReferencesCited [N ggg g UNITED STATES PATENTS P 1,399,423 12/1921 Cunningham 33/206 PM3010214 11/1961 P 11 '1 33/215 Patented June28,l97l Priority Aug. 17,1967 FOREIGN PATENTS France 1,248,887 11/1960 France 118007 1,540,4768/1968 France Primary Examiner Robert B. Hull Attorney-Stevens, Davis,Miller and Mosher APPARATUS FOR DETERMINATION OF THE ORIENTATION OF AMOVING MEMBER, PARTICULARLY A DRILLING HEAD tion of a moving member,such as a drilling head used in well drilling, including a pair ofpendulum units carried by the moving member, each being mountedorthogonally to the 8 Claims 7 Drawmg other and to the vertical axis ofthe member, and each adapted U.S. Cl 33/205, to transmit a signalrepresentative of angular inclination to the /215 horizontal. Anazimuthal direction sensing device provides a Int.Cl G01c 9/16, signalrepresentative of the azimuthal orientation of a pivot E2 1 b 47/00 axisof one of the pendulum units. Calculating means and re- Field of Search..33/215 (.2), lated instrumentation provide a resultant signalrepresentative 215 (.3), 205.5 (E), 205 of the amount and direction ofinclination of the member.

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12, Pi/VDd/L UM ABSTRACT: Apparatus for determining the physicalorienta- PATENTEUJU-28|91| 34587176 sum 1 or 5 PIERRE sum 5R1;

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Q9 Q 3 WW ATTORNEYS PATENTEflJuuzslsn 3.1581176 sum 5 BF 5 INVENTORATTORNEYS APPARATUS FOR DETERMINATION OF THE ORIENTATION OF A MOVINGMEMBER, PARTICULARLY A DRILLING I-IEAD This invention relates to anapparatus or facility which makes it possible to know the direction of aborehole at any time without the need to lower and pull up a recordinginstrument.

Borehole direction can be defined by two anglesthe inclination ofborehole direction to the vertical-i.e., the inclination of the drillinghead to the vertical toand the bearing-Le, the angle which the verticalinclination plane makes with a known fixed horizontal direction which istaken as the datum direction and which is e.g. north.

The invention makes it possible to discover the amount of suchinclination and such bearing from two other directly measurable angles,namely the angles a and B which two reference straight lines, associatedwith the drilling head, make with the horizontal plane, such lines bothbeing perpendicular to the head axis and being perpendicular to oneanother.

Calculation shows that the sine of the inclination of the drilling headaxis relatively to the vertical is obtained by vectorial breakdown ofthe sines of the two angles a and Bi.e., the resultant of two vectorsextending along two straight lines and having the lengths sin a and sin[3 respectively is a vector oflength sin 0 in the vertical planeofinclination of the drilling head (the vertical plane containing thedrilling head axis).

Consequently, if i]; is the angle which such plane makes with the planecontaining the drilling axis and one of the reference straight lines:

sina=sin0cosill (l) sinfi=sin0sin (2) thus completely determining theorientation of the vertical relatively to the drilling headi.e., to thedrilling head axis and to the reference straight lines, from formulas land (2):

sin 0=sin a+sin B (3) sin [3 tan Sin a Angles a and B can be measured bypendulums. Angle a may be determined by a pendulum which oscillates in avertical plane, the plane containing a first reference horizontalstraight line. Then, as the reference line changes its position from ahorizontal position to one of inclination, the pendulum may be taken ashaving rotated relative to that line thru an angle 0:. However, for theplane of oscillation to be vertical the pendulum must be of the kindhaving 2 of freedom-Le, it

must be connected by a first shaft or spindle, called the inner shaft orspindle, to an intermediate member which is connected to the drillinghead by a second shaft or spindle which is called the outer shaft orspindle and which extends parallel to the reference line. With thesystem in the balanced state, the inner shaft is horizontal and theplane of oscillation therearound is vertical.

To determine the bearing, a reference direction associated with thedrilling head, such as the first reference line, is not a proper datumdirection for the reason that torsion of the drilling rod makes theorientation of the drilling head unknown. Also, the angle which thedatum horizontal direction makes with the direction associated with thehead must be measured and this angle 41,, indicates rotation of the headin space. The bearing is then substantially:

z= l l o '11,, being measured by an extra instrument such as a magneticcompass or a directional gyroscope.

The apparatus according to the invention, which is based on theforegoing, comprises in combination two pendulums which have 2 offreedom and which are borne by the drilling head each of which isprovided with an intermediate member or universal joint suspended on thedrilling head around an outer shaft or spindle, and comprises a heavymass oscillating around an inner shaft or spindle borne by theintermediate member, the inner shaft or spindle being perpendicular tothe outer shaft or spindle, the outer shafts or spindles of the twopendulum mountings being perpendicular to one another and also beingboth perpendicular to the drilling head. Resolvers or other inductivetransmitters are disposed one each on the inner shaft of one of thependulums and deliver a signal representing the sine of the angle ofinclination to the horizontal of the outer shaft of the correspondingpendulum. A calculating apparatus receives the signals from thetransmitters of the two pendulums and delivers a signal proportional tothe sine of drilling head inclination to the vertical, such signal beingtransmitted to ground level. A galvanometric indicator measures suchsignal or an indicator comprising a controlled instrument gives theangle of inclination.

The computer also delivers the angle r11 which the vertical plane ofinclination of the drilling head makes with the first reference line. Todetermine the bearing of the vertical plane of inclination of thedrilling head to a datum direction, such as north, the apparatus alsocomprises a directional instrument, such as a magnetic compass or agyroscope, which delivers the angle made by the datum direction with aplane which is associated with the drilling head and which is parallelto the first reference line. The directional instrument is suspended bya universal mounting in such head. The apparatus also comprises adifferential which receives the angle between the vertical plane ofinclination of the drilling head with the first reference line asdelivered by the computer, and the angle indicated by the directionalinstrument, the differential deliverin g the difference between thesetwo angles. Provided that the inclination angle 0 of the drilling headis relatively small, the resulting angle is a good approximation to thebearing.

If the computer delivers the angle ill as rotation of a shaft and if thesignal 41,, transmitted by the directional instrument goes to a repeaterwhich operates a shaft rotating through the angle 41,, the differentialcan be conventional mechanical differential and is then mounted betweenthe two shafts and comprises a third shaft which rotates through th -illand drives an electric transmitter whose signal is transmitted to groundlevel.

Alternatively, the differential can be a differential transmitter whichis disposed on the shaft which the computer rotates through the angle([1 and which receives from the directional instrument electricalsignals representing the angle h indicated by the directionalinstrument. This differential transmitter transmits signals representingthe bearing to ground level.

If drilling head inclination 6 is fairly large, formula (5) becomesinconvenient, for the bearing, in the form of the angle made by thedatum direction with the vertical plane passing through the drillinghead axis, is an angle in the horizontal plane. Also, the angle 41,,between the datum direction and the locating direction associated withthe head is measured in the horizontal plane. To this end, the measuringinstrument, such as a compass, is suspended pendulumfashion and thelocating direction associated with the head, the zero alignment of thecompass, is bound to be horizontal. If the compass suspension were suchthat rotations of the head around its axis caused equal rotations of thecompass casing and of its zero alignment around the vertical, the anglebetween the zero alignment and the vertical plane of inclination of thedrilling axis, such angle being in the horizontal plane, would be equalto the angle ill between the first reference line and such plane ofinclination, and a compass indication would be such that formula (5)would be applicable. Actually, however, the compass ismounted-universally and its indication is not as in the previous casebut is:

l 'fil o in which e denotes the universal-joint error(nonhomokineticity), which increases in proportion as the angle 6increases. Consequently, if the universal joint error is not allowedfor- -and it can be neglected only when the angle 0 is small-what ismeasured is llllll' and so the value obtained for the bearing differsfrom the true value by e.

IfilJ'=1l1e, the azimuth is given correctly by the formula:

The suspension system can be chosen with a view to simplifyingcalculation. For instance, if the compass suspension is devised like thesuspension of a pendulum whose outer shaft is the first reference line,and if the zero alignment direction is parallel to such line when thehead axis is vertical-ie, when the compass indicates the angle of northwith the vertical plane passing through such line, then:

The system further requires an electrical or electromechanical computerwhich can deal with this formula and help to determine ill and whichcan, for instance, comprise tangent calculators of the kind described inthe applicant's French Pat. application No. PV 3390 (8&0) of7 Aug. 1967for Tangent calculating facility."

Each of the pendulums can take the form of a weight suspendeduniversally in a casing containing a high-density liquid, so that theweight of the pendulum mass is substantially compensated for bybuoyancy. In such case, as will be perceived, pendulum density must benonuniform in order to respond as a pendulum under gravity force.

The calculator can take the form of a slave resolver whose two statorwindings in quadrature are connected to the two transmitters disposed onthe inner shafts of the two pendulums so as to produce two AC fields inquadrature whose amplitudes represent the sines of the angles ofhorizontal inclination of the outer shafts of each of the two pendulums,and they therefore produce a resultant field whose amplitude representsthe sine of vertical inclination of the drilling head and whose angleswith the axes of the two stator windings are equal to the verticalangles made by the head with the respective outer shafts of thecorresponding pendulums. The receiver then comprises an amplifier whoseinput receives the signal of a first rotor winding of the resolver, aservomotor energized by the amplifier output and driving the resolvershaft via a reducer, and, if need be, a tachometer generator providingto the amplifier input a signal proportional to the speed of rotorrotation so as to damp motor and resolver movement. Consequently, theresolver rotor is always so positioned that the signal delivered by itsfirst winding remains zero, so that the first winding keeps its axisperpendicular to the resultant field, whereas the second rotor winding,which is in quadrature to the first rotor winding, has its axis parallelto the resultant field and delivers a signal proportional to theamplitude of such field and therefore to the sine of the verticalinclination angle of the drilling head axis. The position of thecontrolled resolver shaft indicates the angle ill since its second rotorwinding, whose axis is parallel to the resultant field, cooperates withthe first stator winding to form an angle reproducing the vertical anglebetween the drilling head axis and the first pendulum outer shaft. Inthe absence of cardan error correction, the resolver shaft is connectedto the differential. If such a corrector is provided, the resolver shaftis connected to the corrector.

An exemplary nonlimitative description of an embodiment of the drillingcontrol apparatus according to the invention is given hereinafter withreference to the accompanying drawings wherein:

FIG. 1 is a diagrammatic sectioned view of the drilling head;

FIG. 2 is a diagrammatic sectioned view of the complete apparatusaccording to the invention;

FIG. 3 is a view of a pendulum sectioned in a plane containing its innersuspension shaft or spindle;

FIG. 4 is a view in section in a plane containing the outer suspensionshaft of the pendulum;

FIG. 5 is the circuit diagram of the apparatus, and

FIG. 6 is the circuit diagram of the connection to a magnetic compass;

FIG. 6a is the diagram of an embodiment including a mechanicaldifferential.

Referring to FIG. I, a drilling head 1 comprises an electric motor 2 fordriving a tool 3. Motor 2 has a hollow shaft 4 connected to a tube 5which forms a drilling rod and which is extended by a flexible tubethrough which liquid goes to shaft 4. The motor is loaded by acylindrical member 6, called the rod weight, which extends like a ringaround the rod. Motor supply wiring 7 extends in the thickness of thewall of tube 5 and of the subsequent flexible tube. 1

The control facility according to the invention has the generalreference 8 and is embedded in the weight 6. Wiring 9 for energizing thefacility 8 and transmitting signals therefrom extends in the thicknessof the wall of a flexible tube just like the motor supply wiring 7.

Referring now more particularly to FIG. 2, the facility 8 comprises atube 10 which helps to protect the facility against high pressure andwhich is hermetically closed at the top by a plug 10a; a lead-throughfor wiring is provided at a place 11.

The tube 10 receives two pendulum units 12a, 12b. The moving part ofeach pendulum unit comprises an inner shaft or spindle l3 pivotallymounted in a skeletonized casing 14 visible in FIGS. 3 and 4. Rotor 15of an inductive transmitter 16a and 16b respectively is rigidly securedto shaft 13, and two hollow members 17 which are FIGS. of revolutionaround the shaft 13 and which are unbalanced by weights 18 are disposedsymmetrically on both sides of the rotor 15.

The casing 14 acts as an intermediate suspension member or gimbal ring.The casing 14 is rotatable, with the interposition of two bearings 20disposed in instrument casing 22 and of two journals 19, around an outershaft or spindle which is perpendicular to the inner shaft or spindle.Casing 22 is filled with a liquid and communicates with expansionbellows 23 for accommodating the expansion of the liquid when thetemperature rises. A cover 24 protects bellows 23. Advantageously, theweights l8 and the density of the liquid are such that the weight of themoving system is exactly compensated for by buoyancy at an averagetemperature.

The outer shafts of the two pendulum units 12a, 12b are bothperpendicular to the axis of the tube 10 and therefore to the drillinghead axis, as well as being perpendicular to one another.

Spiralled wires (not shown) energize rotor winding 25a of transmitter16a from conductors borne by casing 14. The stator 26 of transmitter 16ais borne by casing 14 and has a winding 270 which can be seen in FIG. 5and the windings are so arranged that rotor winding 25a and statorwinding 27a have their field axes perpendicular to one another when theouter suspension shaft is horizontal (a then being zero). Theconnections between the windings of the transmitter 161: and therotating casing 14 are made by way of a number of conductive rings 29disposed on two insulating cylindrical sleeves 21 which are coaxial ofcasing 14 and on which rub sliders 30. Winding 25a is taken to anadjustable tap 31a of an AC supply 31. Tap 31a is adjusted so that thevoltage induced in winding 27a is equal to a voltage taken as unity,defined by another tap 310 of supply 31, when the axes of winding 25aand winding 27a are parallel to one another. Winding 27a thereforedelivers a voltage which, measured with the unit as just defined, isequal to sin a.

Pendulum unit 12b is mounted similarly, its inner shaft or spindle 13being rigidly secured to rotor winding 25b of inductive transmitter 16bwhich is energized from a tap 31b of supply 31, so that stator winding27b of transmitter 16b delivers an AC voltage equal to sin 6 when unityis defined by tap 31c of supply 31.

The inductive transmitters 16a, 16b are connected to a unit 32 (FIG. 2)comprising a resolver 33 having two stator windings 34a, 34b (FIG. 5) inquadrature, winding 34a being connected to winding 27a and winding 34bbeing connected to winding 27b. The rotor of resolver 33 comprises tworotor windings 35a, 35b in quadrature. Winding 35a is connected to theinput of an amplifier 36 whose output energizes a motor 37 driving therotor of resolver 33 via a reducer 37a, said motor, if necessary fordamping purposes, driving a tachometer generator 37b whose output isconnected to the input of the amplifier 36. Motor, reducer andtachometer generator are commonly sold in the same block.

Windings 34a, 34b therefore produce AC fields at right angles to oneanother and with amplitudes representing the signals sin a and sin B.Their resultant has an amplitude representing sin and makes with thedirection of the sin a field an angle equal to the angle ill made by theplane of inclination of the drilling head axis with the outer shaft ofpendulum unit 12a.

The rotor of resolver 33 takes up an angular position such that winding350 has its axis perpendicular to the resultant stator field, thecurrent which energizes motor 37 then being zero. Winding 35b thereforehas its axis extending in the direction of the resultant stator fieldand measures the same exactly. Conductor 38 connected to winding 35btherefore carries a signal representing sin 0; conductor 38 extends inthe thickness of the wall of the flexible tube connected to the drillinghead and energizes an indicating or recording facility at ground level.Another conductor 38a also disposed in the thickness of the tube servesto transmit to ground level the unit voltage delivered by tap 310 ofpower supply 31. if the impedances which the conductors 38, 38a supplyat ground level are equal, currents are proportional to voltages and toline losses. Consequently, the relationship between the two voltages asmeasured at ground level is the same as the relationship between thevoltages transmitted from the boreholei.e., sin 0despite line losses.The voltage supplied via conductor 380 can be used to calibrate agalvanometric indicator or recorder so that the same indicates the sineof the inclination without any line error.

An instrument comprising an inductive sine transmitter can also be usedat ground level, being energized via conductor 38 and delivering, if theunit is the voltage delivered by conductor 38a, a signal equal to thesine of the angle displayed by its rotor. The transmitter is socontrolled that the deviation of this signal from the signal carried byconductor 38i.e., sin 6- stays zero, so that the rotor of thetransmitter indicates the drilling head inclination angle 0 on a linearscale.

Also, the axis of winding 35b makes with the axis of winding 34a anangle equal to the angle 1!; between the plane of inclination of thedrilling head axis and the outer shaft of pendulum unit 12a, and theangle so made is signaled by the rotation angle of resolver shaft 33 andis corrected by a universal joint or cardan error corrector 39 whichdrives through the angle 11: the rotor of a'differential synchro 40.

The stator of synchro generator 40 comprises, as can be seen in FIG. 6,three stator windings 4850 connected to the three stator windings l53 ofa synchro 54 whose rotor is driven by the coupling 55 to the magneticcompass or by a repeater reproducing the indication thereof. The threestator windings 48-50 produce an AC field which makes with the axis ofone of the windings, for instance, the winding 48, the same angle asthedirection of north makes with the axis of the corresponding winding51 of the stator of synchro 54. The compass and its synchro 54 are alsoso adjusted that the field axis of winding 51 which serves as zeroalignment of the compass, is parallel to the outer suspension shaft ofpendulum unit 120. Consequently, the indication transmitted to the threewindings 48-50 of the stator of transmitter 40 represents the angle ill,which north makes with the vertical plane of the outer shaft of pendulumunit 12a, such angle including the cardan error 2. Since the rotor ofthe transmitter 40 has rotated relatively to its stator through theangle ill including the cardan error and thus represents the angle whichthe plane of inclination of the drilling head makes with the outer shaftof pendulum unit 120, one of the windings 5557 of the rotor oftransmitter 40, for instance, the winding 55 makes the angle ill iliwith the stator field. Synchro 40 therefore delivers a signalrepresenting this difference which is the bearing from north of thevertical plane passing through the drilling head axis, synchro 40transmitting such signal to ground level via conductor 58. As previouslyindicated and as shown by FIG. 6a, the position of the resolver shaft 33(corrected in 39) may be transmitted to one sun gear of a mechanicaldifferential 60, the other sun gear of which rotates with the system 55.Thus, the azimuth may be picked up from the planetary carrier of thedifferential and transmitted by a further synchro 61.

The transmitter disposed on the compass need not necessarily be asynchro and can be some equivalent facility, such as a transmitterhaving instead of a rotor a stationary winding combined with a rotatingmagnetic circuit.

The compass need not necessarily comprise a separate transmitter and inthat case is embodied by a facility directly sensitive to the earthsmagnetic field and delivering signals equivalent to the signalsdelivered by a synchro.

If the instrument delivering a directional reference is a gyroscope andnot a magnetic compass, the bearing data, instead of being north, can beany predetermined direction.

The invention must not of course be considered as being limited to theembodiment described and shown but covers all variants. For instance,the computer, the cardan error corrector or some of their parts can bedisposed at ground level and not below ground near the measuringinstruments, in which event the input values of the elements concernedare transmitted to ground level.

Similarly, electrical transmissions with or without slave features canbe used instead of direct mechanical transmissions; conversely,appropriate electrical transmissions can be' used instead of mechanicalconnections. Also, electrical transmissions can, for instance, forinstallation or available power reasons, be supplemented bysupplementary relays or slave systems. For instance, the magneticcompass installation can comprise a repeater which reproduces theindication and drives the transmitter delivering this information to thecomputer.

I claim:

1. An apparatus for determining the physical orientation of a movingmember, of use more particularly for controlling drilling operations,such apparatus comprising two pendulum units, each having outer shaftsor spindles mounted on the moving member along an axis orthogonal to anaxis of the member whose orientation is to be determined, a suspensionmember mounted for rotation about the axis of said shafts or spindles, apendulum and an inner shaft connected to the pendulum and mounted onsaid suspension member for rotation about an axis orthogonal to thefirst-named axis and normally orthogonal to the second named axis; twoinductive transmitters connected each to the inner shaft of one of thependulum units and delivering a signal representing the sine of theangle of inclination from the horizontal of the outer shaft of thecorresponding pendulum; and a calculating device receiving the signalsfrom the two transmitters and providing a signal representing the sineof the angle of inclination from the vertical of the second named axis.

2. The apparatus specified in claim 1 further comprising a cardan errorcorrector which receives said signal from the calculating device andwhich calculates the bearing correction.

3. The apparatus specified in claim 1 wherein each of the pendulum unitscomprises a casing enclosing said suspension member and pendulumcontaining a liquid to reduce the weight of the pendulum on the shaftmountings.

4. The apparatus specified in claim 1 wherein the calculating devicecomprises a resolver having two rotor windings in quadrature and alsotwo stator windings in quadrature which receive, from the twotransmitters disposed on the pendulum inner shafts respectively saidsignals representing the sines of the angles of inclination from thehorizontal of the pendulum outer shafts, the calculating device furthercomprising an amplifier whose input receives the signal from the firstrotor winding of the resolver, a servomotor energized by the amplifieroutput and driving the resolver shaft; the output of the second rotorwinding supplying a signal representing the sine of the said angle ofinclination of the second named axis.

5. The apparatus specified in claim 1 wherein the calculating device isborne by the moving member.

6. The apparatus specified in claim 1 further comprising an azimuthaldirection sensing instrument, which is gimbalmounted in the movingmember; and a differential which receives from the calculating devicethe angle between the vertical plane of inclination of the second namedaxis and the of the azimuthal.

8. The apparatus specified in claim 6 wherein the differential is adifferential synchro whose rotor is disposed on a shaft connected to thecalculator to rotate like the plane of inclination of the moving memberaxis and which receives from the azimuthal direction sensing instrumentsignals representing the azimuthal orientation of a predeterminedtransverse axis fixed in saidmoving member.

UNITED STATES PATENT ()FE1ICE CERTIFICATE OF CORRECTION 3,587,176 DatedJune 28, 1971 Patent No.

Inve t Pierre Schnerb It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

[73] Assignee Association Des Ouvriers En Instruments De Precision,

Signed and sealed this 2nd day of May 1972.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer FORM POI-1050 (IO-69]USCOMM-DC 60376-P69 u 5 GOVERNMENT PRINTING OFFICE 1969 0-356-334

